Killed 1000 AI soldiers

AI soldiers can be found littering the maps during every match. They will respawn via drop pods a short time after they are killed, so there are dozens available to kill during every match. Throw a rocket volley at them while in a Titan to quickly take out a few at once. If you do this every time you're in a Titan, you'll earn this on your way to your 50 wins in every mode.